Fix a race condition where interrupts set up after boot could be enabled in the PIC before the interrupt handler was set. If the interrupt triggered in that window, then the interrupt vector would be disabled.
Fix a race condition where interrupts set up after boot could be enabled in
the PIC before the interrupt handler was set. If the interrupt triggered in
that window, then the interrupt vector would be disabled.

Reported by:	Marco Trillo

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase